1. Field of Invention
The present invention relates to a field of jaw crushers, and more particularly to a jaw crusher with a double-crank-rocker mechanism.
2. Description of Related Arts
In present, the most widely used jaw crusher is compound pendulum jaw crusher, which comprises a swinging jaw and a fixed jaw and simulates the movement of animal's jaw for crushing. The jaw crusher is widely used in mining, smelting, building material, highway, railway, water conservancy and chemical industry for moderately crushing ores and bulk materials.
From a mechanical point of view, the conventional jaw crushers (compound pendulum jaw crushers, the same below), have a common typical structure. That is to say, each of the conventional jaw crushers has a crank-rocker mechanism (an eccentric shaft thereof is a crank, the swinging jaw is a connecting rod, and the bracket is a rocker). A side of the swinging jaw forms a V-shaped crushing chamber with a side of a frame. An upper portion of the swinging jaw directly obtains a horizontal crushing stroke from an eccentric driving shaft. A lower portion of the swinging jaw provides a circular motion by the swinging jaw for driving the bracket to swing in such a manner that a horizontal crushing power stroke and a material discharge stroke are provided. The structure is simple and easy to manufacture, which makes the jaw crusher the most widely used crusher. But the disadvantage is that with the mechanism, the horizontal crushing stroke and the material discharge stroke provided by the swinging bracket driven by an upward pulling force of the swinging jaw contradict the crushing force and the discharge. That is to say, when great crushing capacity is required, the material discharge capacity has a trend of being zero, and when great material discharge capacity is required, the crushing capacity drops dramatically.
The above contradiction is determined by mechanical principle of the structure. Referring to FIG. 1 of the drawings, a sketch view of a conventional jaw crusher is illustrated. The conventional jaw crusher comprises: a frame 1, an eccentric driving shaft 3, a fixed jaw plate 6, a movable jaw plate 5, a front swinging jaw 4, a front bracket 7 and a driving wheel 2. An upper portion of the swinging jaw 4 directly obtains a horizontal crushing stroke from the eccentric driving shaft 3. A lower portion of the swinging jaw 4 drives the bracket front 7 to swing by the eccentric driving shaft 3 in such a manner that a horizontal crushing power stroke and a material discharge stroke are provided. When a transmission angle of the front bracket 7 is maximized (referring to FIG. 3 and FIG. 4 of the drawings) or minimized (referring to FIG. 5 and FIG. 6 of the drawings), a swinging jaw tension F1 and a front bracket thrust F2 form a composition force F3. The F3 can be resolved into a vertical force F5 and a horizontal force F4, wherein the F4 is an effective crushing force. Obviously, the F4 is much smaller than the F1 as long as the transmission angle θ<90°, and a movement of the lower portion of the swinging jaw is always in a state of force reduction effect. In addition, we can see that an upper stop point M2 and a lower stop point M1 of the front swinging jaw forms a horizontal stroke S. A horizontal stroke S1 under the maximized transmission angle is less than a horizontal stroke S2 under the minimized transmission angle. However, the F4 under the maximized transmission angle is greater than the F′4 under the minimized transmission angle.
For a higher yield, discharge stroke may be set to max. Although this is conducive to the discharge of materials, the horizontal crushing force is in a state of max force reduction effect, which is very prejudicial to crushing. This is a contradiction. That is to say, when crushing capacity is high, the material discharge capacity is low; and when material discharge capacity is high, the crushing capacity is low.
Since the jaw crusher was developed, a lot of improvements and innovations have been achieved, and a large number of inventions and utility model patents have been published. But the above disadvantages have not been solved. For example, in Chinese patent ZL 02130566.8, wearing strength of parts is improved and adjustment is easier, but the problem of force reduction effect is not solved.
In Chinese patent ZL 200810043629, the bracket is replaced by a toggle rod. Only the structure and force conditions are changed. And the contradiction of crushing force and discharge still exists.
In short, the movement of the lower portion of the swinging jaw of the conventional jaw crusher is mainly set to discharging. Therefore, the movement of the lower portion of the swinging jaw is material discharge stroke rather than material crushing stroke. Although with a little crushing effect, which is quite little, the power loss is very high (due to the force reduction effect). These are the disadvantages and shortcomings of the conventional jaw crusher.
Mechanical characteristics of the crank-rocker mechanism the conventional jaw crusher determines that working and discharging of the lower portion of the swinging jaw are not compatible with each other. For guaranteeing a certain yield, the transmission angle will be set to min. This results in:
A) the force reduction effect is maximized and crushing function is severely limited; and even jamming will be occurred, which can seriously reduce the crushing effect (and that's why the jaw crusher is a coarse crusher).
B) the force reduction effect causes power loss which reduces the crushing efficiency, or economic efficiency.